A code separating the figure from the judgement, and categories that were chosen anyway.
Is–ought gap
That no description of how things are yields a conclusion about how they ought to be, without something evaluative already smuggled in.
- Theme
- Ethics and character
- Tradition
- Western
- Term fixed
- 1739
In plain terms
You can describe a situation completely and still not have said what anyone should do about it.
That sounds obvious and is constantly violated. Something is natural, so it is good. Most people do it, so it is acceptable. This is how it has always been, so it should continue. Each of those moves from a fact to a value, and none of them is valid as it stands - a further premise about what matters is required, and it is usually invisible precisely because it is shared.
Spotting the move is one of the more useful things philosophy offers, because the missing premise is exactly where the disagreement usually is. Two people arguing about the facts are often not disagreeing about the facts at all.
As a philosopher would put it
Hume's observation is that authors proceed with ordinary reasoning about what is and then, imperceptibly, begin using ought, and that this new relation requires explanation. Whether he intended a logical impossibility or a complaint about carelessness is disputed by scholars, and both readings have been influential.
Moore's naturalistic fallacy is a different claim: that good cannot be defined in terms of any natural property, established by the open question argument - for any proposed definition, it remains an open question whether things so defined are good, which would be closed if the definition were correct.
The standard responses divide. Searle argued that institutional facts bridge the gap - from the fact that someone made a promise, an obligation follows, because promising is constituted by norms. Others accept the gap and locate values elsewhere: expressivism makes evaluative language expressive rather than descriptive, and error theory makes it descriptive and uniformly false. Naturalists deny the gap, holding that some facts about flourishing are evaluative facts.
Where you meet it
The UK Statistics Authority operates a Code of Practice under which official statistics are released independently of ministerial comment, and pre-release access is tightly limited.
The design encodes the gap. The statistician's job is to establish what is the case - unemployment, crime, waiting times - and to say so without evaluation. Whether the figures show a policy succeeding is a separate judgement made by others, and the Authority has publicly criticised ministers who blurred the line, including over the presentation of migration and health-spending figures.
The arrangement is unstable in an instructive way. Deciding what counts as unemployment, which crimes are recorded, and how waiting time is measured are all evaluative decisions embedded in the production of the fact. A statistics agency cannot separate is from ought completely, because the categories are chosen. What it can do is make the choices explicit and separate the reporting from the advocacy - which is the gap handled institutionally rather than solved.
What is actually disputed
Whether the gap holds.
Searle's promising argument is the standard attempt to bridge it: given the institution, the fact that a promise was made entails an obligation. Critics reply that the entailment depends on accepting the institution's norms, which is an evaluative commitment supplied rather than derived.
Neo-Aristotelian naturalists deny the gap differently. If a good X is one that flourishes as an X does, then facts about human flourishing are already evaluative, and the split between fact and value is an artefact of a modern picture of nature as valueless. That has force and requires the account of human function that Aristotle's critics reject.
What is not in dispute is the practical point. The move from natural to good, or from customary to right, is made constantly and is not valid without a further premise - and identifying the premise is usually more productive than arguing about the facts.
Commonly confused with
- the naturalistic fallacy Moore's fallacy concerns defining good in natural terms. Hume's gap concerns deriving ought from is. They are related and not identical, and the conflation is very common.
- facts do not matter The gap says facts alone do not settle what to do. Facts are indispensable to every practical question and settle none of them by themselves.
- the appeal to nature That is one instance of crossing the gap. The gap is the general point of which it is a case.
Defined against
- Moral law A law written into nature needs a route from the fact of nature to the obligation, and this is the argument that no such route exists
Philosophers
- David Hume The original observation
- Immanuel Kant The relocation of ought to reason rather than to nature
- Friedrich Nietzsche The genealogy of values as an alternative to deriving them
- John Stuart Mill The proof of utility that is often cited as committing the fallacy
- Willard Van Orman Quine The naturalising programme that presses against the split
Works
- A Treatise of Human Nature The three sentences
- Principia Ethica The open question argument
- Groundwork of the Metaphysics of Morals Ought grounded in reason instead of fact
- An Introduction to the Principles of Morals and Legislation The framework the objection is often aimed at
- On the Genealogy of Morals Where values are given a history instead of a derivation
Schools
- British Empiricism Where the gap is stated
- Cambridge Analysis Where the naturalistic fallacy is formulated
- Vienna Circle Where evaluative claims are held to describe nothing
- Peripatetic school (Aristotelianism) Where the split is denied
- Classical Pragmatism Where the dichotomy is treated as unhelpful
Related concepts
Value 1887 · Moral law c. 1270 · Objectivity 1781 · Fallibility 1878 · Reason c. 500 BC
Hume's paragraph is three sentences long and does not argue the point so much as observe that authors slide from is to ought without notice; Moore's naturalistic fallacy is a related but distinct claim about definition.